Documentation of the early history of the Ottomans is scarce. According to semilegendary accounts, Ertugrul, khan of the Kayi tribe of the Oguz Turks, took service with the sultan of Rum at the head of a gazi force numbering "400 tents." He was granted territory--if he could seize and hold it--ออออin Bithynia, facing the Byzantine strongholds at Bursa, Nicomedia (Izmit), and Nicaea. Leadership subsequently passed to Ertugrul's son, Osman I (r. ca. 1284-1324), founder of the Osmanli Dynasty--better known in the West as the Ottomans. This dynasty was to endure for six centuries through the reigns of thirty-six sultans (see table 2, Appendix A).

Osman I's small amirate attracted gazis from other amirates, who required plunder from new conquests to maintain their way of life. Such growth gave the Ottoman state a military stature that was out of proportion to its size. Acquiring the title of sultan, Osman I organized a politically centralized administration that subordinated the activities of the gazis to its needs and facilitated rapid territorial expansion. Bursa fell in the final year of his reign. His successor, Orhan (r. 1324-60), crossed the Dardanelles in force and established a permanent European base at Gallipoli in 1354. Murad I (r. 1360-89) annexed most of Thrace (called Rumelia, or "Roman land," by the Turks), encircling Constantinople, and moved the seat of Ottoman government to Adrianople (Edirne) in Europe. In 1389 the Ottoman gazis defeated the Serbs at the Battle of Kosovo, although at the cost of Murad's life. The steady stream of Ottoman victories in the Balkans continued under Bayezid I (r. 1389-1402). Bulgaria was subdued in 1393, and in 1396 a French-led force of crusaders that had crossed the Danube from Hungary was annihilated at Nicopolis (see fig. 5).

In Anatolia, where Ottoman policy had been directed toward consolidating the sultan's hold over the gazi amirates by means of conquest, usurpation, and purchase, the Ottomans were confronted by the forces of the Mongol leader Timur (Tamerlane), to whom many of the Turkish gazis had defected. Timur crushed Ottoman forces near Ankara in 1402 and captured Bayezid I. The unfortunate sultan died in captivity the next year, leaving four heirs, who for a decade competed for control of what remained of Ottoman Anatolia. By the 1420s, however, Ottoman power had revived to the extent that fresh campaigns were undertaken in Greece.

Aside from scattered outposts in Greece, all that remained of the Byzantine Empire was its capital, Constantinople. Cut off by land since 1365, the city, despite long periods of truce with the Turks, was supplied and reinforced by Venetian traders who controlled its commerce by sea. On becoming sultan in 1444, Mehmet II (r. 1444-46, 1451-81) immediately set out to conquer the city. The military campaigning season of 1453 commenced with the fifty-day siege of Constantinople, during which Mehmet II brought warships overland on greased runners into the Bosporus inlet known as the Golden Horn to bypass the chain barrage and 79bfortresssses that had blocked the entrance to Constantinople's harbor. On May 29, the Turks fought their way through the gates of the city and brought the siege to a successful conclusion.

As an isolated military action, the taking of Constantinople did not have a critical effect on European security, but to the Ottoman Dynasty the capture of the imperial capital was of supreme symbolic importance. Mehmet II regarded himself as the direct successor to the Byzantine emperors. He made Constantinople the imperial capital, as it had been under the Byzantine emperors, and set about rebuilding the city. The cathedral of Hagia Sophia was converted to a mosque, and Constantinople--which the Turks called Istanbul (from the Greek phrase eis tin polin , "to the city")--replaced Baghdad as the center of Sunni Islam. The city also remained the ecclesiastical center of the Greek Orthodox Church, of which Mehmet II proclaimed himself the protector and for which he appointed a new patriarch after the custom of the Byzantine emperors.

Data as of January 1995